Lens-fitted photo film unit, flash device, and lens-fitted photo film system

ABSTRACT

A flash device for a lens-fitted photo film unit pre-loaded with unexposed photo film is provided. A main capacitor stores charge. A flash emitter emits flash light. A flash circuit board charges the main capacitor, and drives the flash emitter by discharging the main capacitor in response to an exposing operation. A tightly closed flash case is secured to the lens-fitted photo film unit, for containing the main capacitor, the flash emitter and the flash circuit board. Also, the lens-fitted photo film unit includes a sync switch for generating a trigger signal in response to the exposing operation. Two switch contact points are disposed outside the flash case, for receiving the trigger signal from the sync switch. The two switch contact points disable discharge of the main capacitor while the flash case is away from the lens-fitted photo film unit, and are short-circuited for discharge of the main capacitor upon supply of the trigger signal while the flash case is secured to the lens-fitted photo film unit.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a lens-fitted photo film unit,flash device and lens-fitted photo film system. More particularly, thepresent invention relates to a lens-fitted photo film unit of which aflash device can be used repeatedly by connection with a new lens-fittedphoto film unit after using the initial lens-fitted photo film unit, anda flash device, and a lens-fitted photo film system.

[0003] 2. Description Related to the Prior Art

[0004] A lens-fitted photo film unit is known as a single-use camerapre-loaded with photo film. The lens-fitted photo film unit includes amain body, and front and rear covers. The main body contains photo film,and has a mechanism for taking an exposure. The front and rear coverscover the front and rear of the main body. Those relevant parts areformed from plastic material.

[0005] The lens-fitted photo film unit has typical features of a smallsize, a simple structure, a low cost and the like. However, there areadditional structures provided in the lens-fitted photo film unit forvarious purposes, for example, a flash type of the lens-fitted photofilm unit. The flash type has a flash device, which includes a flashemitter and a flash circuit board supplied with power by a battery.

[0006] After a user exposes all the frames on the photo film, he or sheforwards a used lens-fitted photo film unit to a photo finisher or photolaboratory without disassembly, and requests printing. When photographicprints are obtained, the developed photo film is also returned to theuser. A housing of the used lens-fitted photo film unit, in contrast, iscollected, handled by a photo finisher, and withdrawn to a cameramanufacturer.

[0007] There are suggestion of the camera manufacturer for recycling theused lens-fitted photo film unit in view of preventing environmentalpollution and utilizing resources. A circulation type of manufacturingsystem has been created by designing numerous processes including adesign of a product and a manufacturing line specifically inconsideration of the recycling.

[0008] The camera manufacturer disassembles the used lens-fitted photofilm unit. The flash device and exposure unit are cleaned, inspected andthen reused. Plastic parts are melted and pelletized, and regenerated asplastic material. The lens-fitted photo film unit is originallyconstructed for a single use. To keep its cost low, durability of partsof the lens-fitted photo film unit is considerably low in comparisonwith parts used in a widely used camera. For the flash device and otherparts to be reused, quality is maintained by suitable inspection andrepair if desired.

[0009] The recycling is also effective in lowering a market price of thelens-fitted photo film unit. Among the various parts of the lens-fittedphoto film unit, the flash device is remarkably expensive. The reuse ofthe flash device is highly advantageous for the purpose of lowering thecost of the lens-fitted photo film unit.

[0010] However, withdrawal of products of the used lens-fitted photofilm unit to the camera manufacturer is not complete. There is adistribution of part of all the products of the used lens-fitted photofilm unit to third parties, such as photo film reloading dealers,part-reusing dealers and the like. The reloading dealers load the usedlens-fitted photo film unit with unexposed photo film. The part-reusingdealers utilize the used lens-fitted photo film unit, obtains partsconstituting the main body, and assembles the lens-fitted photo filmunit as a newly created product. The reloaded products and part-reusedproducts are packaged, and marketed as unused products. A price of thoseis very inexpensive, because the flash device in the reloaded productsor part-reused products is originally obtained without a costly process.

[0011] However, the reloaded products or the part-reused products arelikely to have great problems in the quality because the parts are notcleaned, repaired or inspected suitably. Such problems may cause damagesto reputation of the lens-fitted photo film unit with good performance,and also reputation of the camera manufacturer of the lens-fitted photofilm unit.

[0012] In the case of the unsuitable reuse of parts, only limited parts,such as flash device, are reused for the reason of high cost and greatease in operation for the reuse. Remaining parts other than the flashdevice or the like are likely to be discarded in spite of muchpossibility of reuse. If the unsuitable reuse of parts is continued on alarge scale, there is no achievement of purposes of the circulation typeof the manufacturing system established by the camera manufacturer, thepurposes being for prevention of environmental pollution, effectiveutilization of resources, and the like. Furthermore, advantages of a lowcost caused by the reuse cannot be obtained. It may cause failure anddestruction of the circulation type of the manufacturing system.

[0013] JP-A 7-120883 discloses examples of preventing unsuitablereloading of photo film on the side of the camera manufacturer. Some ofthe examples has been worked and used. However, there is no knowntechnique of preventing unsuitable reuse of flash device and otherrelevant parts of the used lens-fitted photo film unit.

SUMMARY OF THE INVENTION

[0014] In view of the foregoing problems, an object of the presentinvention is to provide a lens-fitted photo film unit of whichunsuitable reuse of parts can be suppressed or prevented according todistribution of used products of lens-fitted photo film units, and aflash device, and a lens-fitted photo film system.

[0015] Another object of the present invention is to provide alens-fitted photo film unit of which a flash device can be usedrepeatedly by connection with a new lens-fitted photo film unit afterusing the initial lens-fitted photo film unit, and a flash device, and alens-fitted photo film system.

[0016] In order to achieve the above and other objects and advantages ofthis invention, a flash device for a lens-fitted photo film unitpre-loaded with unexposed photo film is provided. A main capacitorstores charge. A flash emitter emits flash light. A flash circuit boardcharges the main capacitor, and drives the flash emitter by dischargingthe main capacitor in response to an exposing operation. A tightlyclosed flash case is secured to the lens-fitted photo film unit, forcontaining the main capacitor, the flash emitter and the flash circuitboard.

[0017] Furthermore, a battery is contained in the flash case, forsupplying the flash circuit board with power.

[0018] The lens-fitted photo film unit includes a sync switch forgenerating a trigger signal in response to the exposing operation.Furthermore, first and second switch contact points are disposed outsidethe flash case, for receiving the trigger signal from the sync switch.

[0019] The first and second switch contact points disable discharge ofthe main capacitor while the flash case is away from the lens-fittedphoto film unit, and are short-circuited for discharge of the maincapacitor upon supply of the trigger signal while the flash case issecured to the lens-fitted photo film unit.

[0020] The flash emitter includes a flash discharge tube, and a triggerelectrode for trigger of the flash discharge tube. Furthermore, atrigger capacitor is charged by the flash circuit board. A triggertransformer has primary and secondary windings, the primary windingbeing connected with the trigger capacitor, the secondary winding beingconnected with the trigger electrode, operated upon discharge of thetrigger capacitor, for outputting high voltage obtained by boostingvoltage across the trigger capacitor. A trigger switch has the first andsecond switch contact points, connected with a common terminal of theprimary and secondary windings in the trigger transformer, closed inresponse to the trigger signal, for discharging the trigger capacitorvia the primary winding.

[0021] The flash circuit board includes a memory for storing informationof a useful life flashing time number of times of emitting flash lightin the flash emitter, the useful life flashing time number beingpredetermined smaller than a number of times of emitting flash lightaccording to part useful life of the flash emitter or the flash circuitboard. A counter counts a flashing time number of times of emittingflash light in the flash emitter. A switching circuit inhibits operationof the flash emitter in response to reach of the flashing time number tothe useful life flashing time number.

[0022] Furthermore, a display device displays information of a presentflash usability according to the flashing time number and the usefullife flashing time number.

[0023] The flash usability information comprises a number of usabletimes according to a difference of the useful life flashing time numberand the flashing time number.

[0024] In a preferred embodiment, the flash usability informationrepresents one of first to Nth steps of a number of usable timesaccording to a difference of the useful life flashing time number andthe flashing time number, and the first step comprises a range includinga highest level of the usable time number, and the first to Nth stepsare determined in sequentially decreasing manner of the usable timenumber toward a lowest level thereof.

[0025] The lens-fitted photo film unit includes a housing connectionpanel opposed to the flash case, and having a receiving opening.Furthermore, a retention projection is formed to project from a caseconnection panel of the flash case opposed to the housing connectionpanel, fitted in the receiving opening, for retaining the caseconnection panel on the housing connection panel.

[0026] The receiving opening includes a first gap portion. A second gapportion is disposed to extend from the first gap portion, and having asize equal to or more than the first gap portion. The retentionprojection includes a first portion, disposed to project from the caseconnection panel, having a size equal to or less than the first gapportion, for being inserted therein. A second portion is disposed toproject from an end of the first portion in a direction of increasing awidth thereof, engaged with an inner face of the first gap portion, forpreventing drop of the first portion, the second portion having a sizeequal to or less than the second gap portion, for being inserted in thesecond gap portion before setting of the first portion in the first gapportion.

[0027] After insertion into the second gap portion, the second portionis set in the first gap portion by sliding or rotating the retentionprojection relative to the receiving opening.

[0028] In another preferred embodiment, the lens-fitted photo film unitincludes a shutter mechanism, having a shutter blade, for providing thephoto film with exposure. First and second blade checking light guidesare disposed so that the shutter blade is between an output end of thefirst light guide and an input end of the second light guide, the firstand second light guides being changed over between optical interceptingand optical transmitting states according to a shift of the shutterblade. The flash circuit board includes a sync light-emitting unit,disposed outside the flash case, opposed to an input end of the firstlight guide, for outputting a signal of light, and sending the signal oflight toward the shutter blade. A sync light-receiving unit is disposedoutside the flash case, opposed to an output end of the second lightguide, for detecting the signal of light incident thereon in light guidechangeover between the intercepting and transmitting states, andgenerating the trigger signal in synchronism with opening/shutting ofthe shutter blade.

[0029] Furthermore, a charge allowing switch is changed over in responseto connection and detachment between the flash case and the lens-fittedphoto film unit, to allow charging operation of the flash circuit boardupon connection of the flash case, and to inhibit charging operation ofthe flash circuit board upon detachment of the flash case.

[0030] Furthermore, a forcible discharging switch is connected with themain capacitor, for being changed over in response to connection anddetachment between the flash case and the lens-fitted photo film unit,to allow charging operation of the main capacitor upon connection of theflash case, and forcibly to discharge the main capacitor upon detachmentof the flash case.

[0031] The forcible discharging switch includes a pair of contactpoints. A movable switch segment is positioned on the contact pointswhen the flash case is away from the lens-fitted photo film unit, toshort-circuit the contact points. The lens-fitted photo film unitpresses the switch segment when the flash case is connected therewith,for disconnecting the switch segment from at least one of the contactpoints.

[0032] In still another preferred embodiment, the forcible dischargingswitch includes a pair of contact points. A movable switch segment ispositioned on the contact points when the flash case is away from thelens-fitted photo film unit, to short-circuit the contact points. Afirst magnet is secured to the switch segment, and opposed to thelens-fitted photo film unit. The lens-fitted photo film unit includes asecond magnet, set at the first magnet when the flash case is connectedtherewith, for magnetically repelling and shifting the first magnet, todisconnect the switch segment from at least one of the contact points.

[0033] In another preferred embodiment, the flash emitter includes aflash discharge tube, and a trigger electrode for trigger of the flashdischarge tube. Furthermore, a trigger capacitor is charged by the flashcircuit board. A trigger transformer has primary and secondary windings,the primary winding being connected with the trigger capacitor, thesecondary winding being connected with the trigger electrode, operatedupon discharge of the trigger capacitor, for outputting high voltageobtained by boosting voltage across the trigger capacitor. A triggerswitching element has first and second terminals and a gate, the firstterminal being connected with a common terminal of the primary andsecondary windings in the trigger transformer. An external switch hasfirst and second switch contact points, connected with the gate of thetrigger switching element, closed in response to the trigger signal, forapplying voltage to the gate to render the first and second terminalsconductive, whereby the trigger capacitor is discharged via the primarywinding.

[0034] In still another preferred embodiment, the flash circuit includesfirst and second battery connection terminals. The battery includesfirst and second battery electrodes, disposed to extend in one commondirection, and connected with respectively the first and second batteryconnection terminals fixedly.

[0035] According to another aspect of the invention, a lens-fitted photofilm system is provided, and includes a lens-fitted photo film unit, anda flash device for emitting flash light in exposure in the lens-fittedphoto film unit. The lens-fitted photo film unit includes a housingpre-loaded with unexposed photo film. An attaching portion in apredetermined shape is formed with the housing and adapted to flashattachment. A battery is contained in the housing. A first terminal ispositioned outside the housing, for supplying power from the battery.The flash device includes a connection panel connectable with theattaching portion in a removable manner. A powering terminal ispositioned outside the connection panel, connected with the firstterminal, for supplying power to emit flash light.

[0036] The housing is box-shaped, and has a front panel, a rear panel,and first and second lateral panels. The first lateral panel is opposedto the flash device, and has the attaching portion.

[0037] The lens-fitted photo film unit further includes a sync switch,incorporated in the housing, for generating a trigger signal in responseto an exposing operation. A second terminal is disposed beside the firstterminal, for outputting the trigger signal from the sync switch. Theflash device further includes a trigger terminal, disposed beside thepowering terminal, and connected with the second terminal.

[0038] The first and second terminals are male terminals. The triggerterminal and the powering terminal are female terminals.

[0039] The connection panel includes an engaging portion, engaged withthe attaching portion, for retaining the first lateral panel.

[0040] The attaching portion includes an engaging projection, and theengaging portion includes an engaging recess.

[0041] The attaching portion further includes at least one positioningridge disposed to project from an edge of the engaging projection. Theengaging portion further includes at least one positioning notch, formedin an edge of the engaging recess, and engaged with the positioningridge.

[0042] According to still another aspect of the invention, a lens-fittedphoto film unit includes a housing pre-loaded with unexposed photo film.A flash device emits flash light. An attaching portion in apredetermined shape is formed with the housing, and adapted to securingof the flash device in a removable manner. The attaching portion is usedfor securing a dummy block in producing a daylight type lacking theflash device.

[0043] The flash device includes a flash emitter for emitting flashlight upon discharge. A flash circuit board drives the flash emitter inresponse to an exposing operation. A battery supplies the flash circuitboard with power. A tightly closed flash case contains the flashemitter, the flash circuit board and the battery.

[0044] The housing includes a main body. At least one outer cover issubstantially box-shaped, has front and rear panels, for covering themain body. The attaching portion comprises a recess, formed in the outercover, disposed in at least the front panel, for receiving the flashdevice fitted therein.

[0045] The at least one outer cover includes a front cover having thefront panel. A rear cover has the rear panel.

[0046] The front panel has upper and lower side lines, and first andsecond lateral side lines. The recess is positioned to extend from apart of the upper side line to a part of the first lateral side line.

[0047] The recess and the flash device are L-shaped as viewed from theupper side line toward the lower side line.

[0048] In another preferred embodiment, the recess and the flash deviceare substantially box-shaped.

[0049] According to an additional aspect of the invention, a lens-fittedphoto film unit pre-loaded with unexposed photo film includes a maincapacitor for storing charge. A flash emitter emits flash light. A flashcircuit board charges the main capacitor, and drives the flash emitterby discharging the main capacitor in response to an exposing operation.A tightly closed flash case contains the main capacitor, the flashemitter and the flash circuit board.

[0050] Furthermore, a main body is pre-loaded with the unexposed photofilm. An outer cover covers an outside of the main body. A battery iscontained in the flash case, for supplying the flash circuit board withpower. The flash case has a surface disposed to extend from an outersurface of the outer cover.

[0051] In still another preferred embodiment, furthermore, a main bodyis pre-loaded with the unexposed photo film. An outer cover covers anoutside of the main body. A battery is contained in the flash case, forsupplying the flash circuit board with power. The flash case is formedwith an inner surface of the outer cover.

[0052] Consequently, a flash device can be used repeatedly by connectionwith a new lens-fitted photo film unit after using the initiallens-fitted photo film unit, because of the construction of the flashdevice externally connectable with the lens-fitted photo film unit.

[0053] Also, unsuitable reuse of parts can be suppressed or preventedaccording to distribution of used products of lens-fitted photo filmunits, because distribution of used flash devices can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The above objects and advantages of the present invention willbecome more apparent from the following detailed description when readin connection with the accompanying drawings, in which:

[0055]FIG. 1A is a perspective illustrating a lens-fitted photo filmunit with an externally connectable flash device;

[0056]FIG. 1B is an exploded perspective illustrating the lens-fittedphoto film unit and the flash device;

[0057]FIG. 2 is an exploded perspective illustrating the same as FIG. 1Bbut in which a sync switch in the lens-fitted photo film unit is viewed;

[0058]FIG. 3 is an exploded perspective illustrating the lens-fittedphoto film unit;

[0059]FIG. 4 is a circuit diagram illustrating a flash circuit in thelens-fitted photo film unit;

[0060]FIG. 5 is an explanatory chart illustrating processes ofdistribution of the lens-fitted photo film unit and the flash device;

[0061]FIG. 6A is an exploded perspective illustrating another preferredembodiment with a flash device connectable with a bayonet mechanism;

[0062]FIG. 6B is a section, partially broken, illustrating the bayonetmechanism of FIG. 6A;

[0063]FIG. 7A is an exploded perspective illustrating a preferredembodiment a trigger signal of light is used and treated by a synclight-emitting unit and sync light-receiving unit in a flash device;

[0064]FIG. 7B is a block diagram illustrating a flash circuit in theflash device of FIG. 7A;

[0065]FIG. 8A is a perspective illustrating another preferred flashdevice with a residue display panel;

[0066]FIG. 8B is a perspective illustrating an embodiment with aresidual amount indicator;

[0067]FIG. 9 is a circuit diagram illustrating a flash circuit of theflash device of FIG. 8A;

[0068]FIG. 10 is a flow chart illustrating a process of counting andcontrolling flash emission;

[0069]FIG. 11A is a block diagram illustrating a flash device having acharge allowing switch and a forcible discharging switch;

[0070]FIG. 11B is a table illustrating states of the switches;

[0071]FIG. 12A is a section, partially broken, illustrating the switchesand a relevant mechanism;

[0072]FIG. 12B is a section, partially broken, illustrating the same asFIG. 12A but in a state the flash device is moved away;

[0073]FIG. 13A is an explanatory view in elevation, illustrating anotherpreferred set of switches with which magnets are used;

[0074]FIG. 13B is an explanatory view in elevation, illustrating thesame as FIG. 13A but in a state the flash device is moved away;

[0075]FIG. 14 is a circuit diagram illustrating a flash circuit in whicha trigger switching thyristor is associated with a trigger circuit;

[0076]FIG. 15 is a side elevation illustrating another preferred batterythat is an electrode pin type;

[0077]FIG. 16A is a perspective illustrating another preferredlens-fitted photo film unit with which a flash device is electricallyconnected by four terminals;

[0078]FIG. 16B is an exploded perspective illustrating the same as FIG.16A;

[0079]FIG. 17 is an exploded perspective illustrating the same as FIG.16B but where terminals of the flash device are viewed;

[0080]FIG. 18 is a section, partially broken, illustrating thelens-fitted photo film unit of FIG. 17;

[0081]FIG. 19 is an exploded perspective illustrating the lens-fittedphoto film unit of FIG. 17;

[0082]FIG. 20 is a circuit diagram illustrating circuits in thelens-fitted photo film unit of FIG. 17;

[0083]FIG. 21A is a perspective illustrating a lens-fitted photo filmunit with which a unit of a flash device is connected;

[0084]FIG. 21B is a perspective illustrating a lens-fitted photo filmunit with which a dummy block is attached;

[0085]FIG. 22 is an exploded perspective illustrating the same as FIGS.21A and 21B in a state of exchanging the flash device and the dummyblock;

[0086]FIG. 23 is an exploded perspective illustrating the same as FIG.22;

[0087]FIG. 24 is a horizontal section illustrating the lens-fitted photofilm unit of FIG. 21A;

[0088]FIG. 25 is an exploded perspective illustrating another preferredlens-fitted photo film unit in which a flash device and a dummy blockare box-shaped;

[0089]FIG. 26 is a horizontal section illustrating the lens-fitted photofilm unit of FIG. 25;

[0090]FIG. 27A is a horizontal section illustrating another preferredembodiment having a flash case formed with a front cover; and

[0091]FIG. 27B is a horizontal section illustrating a dummy front coverinstead of the flash-formed front cover.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) OF THE PRESENTINVENTION

[0092] In FIGS. 1A and 1B, a lens-fitted photo film unit 10 isillustrated, and has a mechanism for taking an exposure and ispre-loaded with photo film. An external type of flash device 11 can besecured to the lens-fitted photo film unit 10 in a removable manner. Itis possible with the flash device 11 to take an exposure according toflash photography with flash light.

[0093] The lens-fitted photo film unit 10 is a single-use device inwhich the photo film is used only for one time. The flash device 11, incontrast, is a repeatedly usable device for plural strips of the photofilm. A user can renew the lens-fitted photo film unit 10, to use theflash device 11 for plural times.

[0094] In FIG. 2, a housing connection panel 12 is included in thelens-fitted photo film unit 10, and adapted for connection with theflash device 11. A receiving opening 12 a as first gap portion is formedin the housing connection panel 12. A retention projection 13 projectsfrom the flash device 11, and is engaged with the receiving opening 12 ato secure the flash device 11 fixedly to the lens-fitted photo film unit10.

[0095] The receiving opening 12 a has such a shape that its rear endportion is smaller than its front end portion. The retention projection13 has a T-shape as viewed in section, and includes upper and lowertongue portions. The retention projection 13 is inserted in the frontend portion of the receiving opening 12 a. The flash device 11 is slidin the backward direction in this state, to engage the tongue portionswith the rear end portion of the receiving opening 12 a. The flashdevice 11 is secured to the lens-fitted photo film unit 10.

[0096] A protective cover 14 is used when the flash device 11 is notattached, and covers the receiving opening 12 a in a closed form. Theprotective cover 14 prevents entry of dust, dirt or the like through thereceiving opening 12 a into the lens-fitted photo film unit 10. Notethat a packing can be used on a lateral face of the flash device 11 inorder to prevent entry of dust or the like through the receiving opening12 a when the flash device 11 is mounted on the lens-fitted photo filmunit 10. Also, a magnet can be used to retain the flash device on thelens-fitted photo film unit.

[0097] A front panel of the lens-fitted photo film unit 10 includes aviewfinder objective window 18 and an opening 17 where a taking lens 16appears. An upper panel of the lens-fitted photo film unit 10 isprovided with a shutter release button 19 and a frame counter 21. Aportion of a winder wheel 22 appears externally in a rear panel of thelens-fitted photo film unit 10.

[0098] In FIG. 3, the lens-fitted photo film unit 10 is constituted by amain body 23, a photo film cassette 26, a front cover 31, and a rearcover 32. The photo film cassette 26 includes photo film 24 and acassette shell 25. The front and rear covers 31 and 32 as outer coverscover the main body 23 with the photo film cassette 26. An exposure unit33 is included in the main body 23. A cassette holder chamber 23 a and aroll holder chamber 23 b are so disposed that the exposure unit 33 liesbetween those. The cassette holder chamber 23 a contains the cassetteshell 25. The roll holder chamber 23 b contains a roll of the photo film24 after being unwound from the cassette shell 25. The winder wheel 22is disposed on the upside of the cassette holder chamber 23 a.

[0099] A shaft (not shown) protrudes from a lower face of the winderwheel 22, and engaged with a spool in the cassette shell 25. A trailingend of the photo film 24 is inserted in a slit in the spool, andretained. When the winder wheel 22 rotates, the spool rotates to advancethe photo film 24.

[0100] The exposure unit 33 includes a light-shielded tunnel 38, ashutter blade 39 as shutter mechanism, and a shutter-cover/lens-holder41. The shutter blade 39 is disposed in front of the light-shieldedtunnel 38. The shutter-cover/lens-holder 41 covers the front of thelight-shielded tunnel 38 and the shutter blade 39. An exposure opening38 a is formed in a front face of the light-shielded tunnel 38, andintroduces light from an object into the light-shielded tunnel 38. Anexposure aperture is formed in the rear of the light-shielded tunnel 38,and defines an exposed region on the photo film 24. An aperture stopopening is formed in the shutter-cover/lens-holder 41. The taking lens16 is held in the shutter-cover/lens-holder 41.

[0101] There is a viewfinder mechanism disposed higher than the exposureunit 33, and having objective and eyepiece lens elements. A framecounter mechanism is disposed also higher than the exposure unit 33, forindicating the number of remaining available frames on the photo film24.

[0102] The shutter blade 39 is pivotally movable between open and shutpositions, and when in the open position, opens the exposure opening 38a, and when in the shut position, allows the exposure opening 38 a toopen. A spring biases the shutter blade 39 toward the shut position. Aknocking mechanism is disposed on the upside of the exposure unit 33,for knocking the shutter blade 39. When the winder wheel 22 is rotatedto wind the photo film 24 by one frame, the knocking mechanism ischarged. When the shutter release button 19 is depressed, the knockingmechanism responsively knocks the shutter blade 39. Accordingly, theshutter blade 39 moves back and forth at one time between the open andshut positions.

[0103] A sync switch 43 is disposed on an upper portion of thelight-shielded tunnel 38. The sync switch 43 outputs a trigger signal insynchronism with releasing of a shutter mechanism, and sends the triggersignal to the flash device 11, and includes a pair of sync switchsegments 43 a and 43 b of metal. A depression portion is formed with theshutter blade 39, for depressing one of the sync switch segments 43 aand 43 b to contact those with one another. When the shutter blade 39comes to the open position, the sync switch 43 is turned on to send thetrigger signal to the flash device 11.

[0104] The sync switch segments 43 a and 43 b are fixed on the main body23. A first end of the sync switch segments 43 a and 43 b is disposedclose to the shutter blade 39. A second end of the sync switch segments43 a and 43 b extends on an outer surface of the roll holder chamber 23b and toward a lateral panel. This second end is disposed on the housingconnection panel 12. A pair of connection terminals 44 a and 44 b astrigger switch or external switch are fixed on the retention projection13 of the flash device 11. When the flash device 11 is secured to themain body 23, the second end of the sync switch segments 43 a and 43 bcontacts each of the connection terminals 44 a and 44 b.

[0105] The front and rear covers 31 and 32 are secured to the front andrear of the main body 23, to cover the lens-fitted photo film unit 10light-tightly. Lower lids 32 a and 32 b are included in the rear cover32, and cover lowest portions of the cassette shell 25 and the photofilm 24. After exposures are taken, the lower lid 32 a is opened forremoving the cassette shell 25.

[0106] The flash device 11 is constituted by a flash circuit board 46, aflash emitter 47, a dry battery 48 and a flash case 49. The flashcircuit board 46 has a circuit pattern printed on a substrate, andincludes various circuit elements in which a main capacitor 45 isincluded. The flash emitter 47 has a xenon discharge tube, a reflector,a diffusing plate and the like. The dry battery 48 supplies thoseelements with power. The flash case 49 contains any of those elements.For those parts to be assembled in the flash device 11, parts of a flashbuilt-in type of lens-fitted photo film unit known in the prior art canbe used. Furthermore, parts with as good performance and as highdurability as those of the flash built-in type may be used. This mannerof the use makes it possible to lower the manufacturing cost.

[0107] As is described heretofore, the flash device 11 can be used fortimes corresponding to plural strips of the photo film. However, thedurability of parts of the flash device 11 is low in comparison with awidely used type of flash device for a camera in view of lowering thecost. If a user continues to use the flash device 11 beyond its usefullife, he or she may be subjected to unexpected damages due to a decreasein the quality.

[0108] Therefore, the capacity of the dry battery 48 is predetermined ata level to prevent a user from using the flash device 11 over the usefullife or period of durability of the parts. The flash case 49 is closedhermetically to keep the parts unremovable, the parts including the drybattery 48, the flash circuit board 46, the flash emitter 47. The drybattery 48 cannot be exchanged by a user. Once the dry battery 48 isused up, the flash device 11 must be discarded without further use. Itis possible to lower the cost of the flash device 11 and ensure the highquality of the product.

[0109] The flash device 11 after being used is withdrawn by a photofinisher to a camera manufacturer, and recycled, in a similar manner tothe lens-fitted photo film unit 10. The camera manufacturerdisassembles, cleans and inspects the flash device 11, and reuses itsparts after renewal or repair as required. The dry battery 48 isrecycled by a specialized dealer.

[0110] A diffusing plate for the flash emitter 47 appears externally infront of the flash case 49. A sliding button 51 is disposed under thediffusing plate. A charger switch of the flash circuit is associatedwith the sliding button 51. The sliding button 51 is slidable between onand off positions, and when in the on position, turns on the chargerswitch to start charging, and when in the off position, turns off thecharger switch to stop charging.

[0111] A readiness indicator 52 is disposed in an upper panel of theflash case 49 for informing that charging is completed to stand by foran exposure. An example of the readiness indicator 52 is a light guidefor optically guiding light from an LED (light-emitting diode) on theflash circuit. Note that the readiness indicator 52 may be disposedbehind the flash case 49. Also, the readiness indicator 52 may be linkedwith the sliding button 51, and when the sliding button 51 is in the onposition, may protrude from the outer surface of the flash case 49, andwhen the sliding button 51 is in the off position, may be contained inthe flash case 49.

[0112] An information label or sticker 53 is attached to a caseconnection panel of the flash case 49, and disposed higher than theretention projection 13. An amount of light emitted by the flash device11 is determined according to various factors including the speed of thephoto film 24, an f-number of the taking lens and the like. Theinformation sticker 53 includes printed information of the speed of thephoto film 24, the f-number of the taking lens and the like associatedwith the flash device 11. As the flash device 11 is the externallyconnectable type, it is possible for a user to check the information onthe information sticker 53 specially if he or she buys the lens-fittedphoto film unit 10 separately. This enables him or her to select asuitable type of the lens-fitted photo film unit 10 as the informationsticker 53 can be checked easily.

[0113] Examples of the dry battery 48 are an alkali manganese battery, alithium battery, and the like of 1.5 volts between electrodes. Capacityof the dry battery 48 is determined at such a small level that flashemission is possible for all frames of two strips of the photo film. Ingeneral, there is small possibility of emitting flash light for all theframes in each photo film strip in consideration of statistics. Eventhis small level of the capacity is sufficient for exposing frames forthree photo film strips. It is naturally possible to determine thecapacity of the dry battery 48 further in view of the useful life of therelevant parts or the like.

[0114] In FIG. 4, circuit arrangement of a flash circuit 56 isillustrated. A charger switch 57 is constituted by three contact points59 a, 59 b and 59 c and a movable segment 58. A first end of the movablesegment 58 is connected with the third contact point 59 c. When thesliding button 51 is shifted to the on position, second ends of themovable segment 58 come in contact with the contact points 59 a and 59b, electrically to interconnect the contact points 59 a, 59 b and 59 c.

[0115] There are an oscillation transistor 61 of an n-p-n type and anoscillation transformer 62, a combination of which constitutes a booster63 operating according to blocking oscillation. Voltage output by thedry battery 48 is converted by the booster 63 to as high voltage as 300volts, to charge the main capacitor 45. The oscillation transformer 62includes a primary winding 62 a, a secondary winding 62 b and a tertiarywinding 62 c combined in mutual induction. A first end of the primarywinding 62 a is connected with a positive electrode of the dry battery48. A second end of the primary winding 62 a is connected with acollector of the oscillation transistor 61. A first end of the secondarywinding 62 b is connected with an anode of a rectification diode 66. Asecond end of the secondary winding 62 b is connected with a positiveelectrode of the dry battery 48 together with a first end of thetertiary winding 62 c. A second end of the tertiary winding 62 c isconnected via a resistor 67 a with the third contact point 59 c of thecharger switch 57.

[0116] A cathode of the rectification diode 66 is connected with oneterminal of a trigger capacitor 68 via a resistor 67 b, and also withone terminal of the main capacitor 45 on the positive side. A secondterminal of the trigger capacitor 68 is connected with the contact point59 a of the charger switch 57. An emitter of the oscillation transistor61 is connected with a negative electrode of the dry battery 48. A baseof the oscillation transistor 61 is connected with the contact point 59b via a resistor 67 c.

[0117] A trigger transformer 69 includes a primary winding 69 a and asecondary winding 69 b combined in mutual induction. A first end of theprimary winding 69 a is connected with a terminal of the triggercapacitor 68. A first end of the secondary winding 69 b is connectedwith a trigger electrode 72, which is disposed close to a flashdischarge tube 71 incorporated in the flash emitter 47. Second ends ofthe primary and secondary windings 69 a and 69 b are combined as onecommon terminal, which is connected with the charger switch 57 via thesync switch 43. Electrodes of the flash discharge tube 71 are connectedwith terminals of the main capacitor 45 in a parallel form.

[0118] A series of the elements including the trigger capacitor 68, theprimary winding 69 a, the sync switch 43, the charger switch 57 and thenthe trigger capacitor 68 constitutes a trigger circuit 64, by which acurrent from the trigger capacitor 68 upon discharge is caused to flowin the primary winding 69 a upon turning on the sync switch 43.

[0119] When the charger switch 57 is turned on, the oscillationtransistor 61 becomes conductive, to cause a current to flow in theprimary winding 62 a as a collector current of the oscillationtransistor 61. In the secondary winding 62 b, there occurs electromotiveforce according to a ratio between the numbers of the turns in theprimary and secondary windings 62 a and 62 b. An output current in thesecondary winding 62 b flows as a base current to the oscillationtransistor 61. In other words, feed forward operation of the oscillationtransformer 62 causes oscillation, and increases a collector current inthe oscillation transistor 61. The output current generated in thesecondary winding 62 b flows also to the main capacitor 45 and thetrigger capacitor 68, to charge both of those.

[0120] There is an LED (light-emitting diode) 74 as sync light-emittingunit, having an anode and cathode connected with terminals of thetertiary winding 62 c in parallel. When the voltage across the maincapacitor 45 being charged comes up to a predetermined voltage level,voltage across the tertiary winding 62 c comes up above a predeterminedlevel, to drive the LED 74. Light emitted by the LED 74 is guided by alight guide to the readiness indicator 52.

[0121] The sync switch 43 is turned on in the state of fully chargingthe main capacitor 45. Then the trigger circuit 64 is closed, to cause acurrent of discharge of the trigger capacitor 68 to flow in the primarywinding 69 a. In response to this, a trigger voltage is output in thesecondary winding 69 b at a high level, and is applied to the flashdischarge tube 71 by the trigger electrode 72. The main capacitor 45 isdischarged in a path with the flash discharge tube 71, in which chargepasses to emit flash light.

[0122] Note that it is possible to combine an auto-cutting circuit withthe flash circuit for preventing a restart of charging typically uponoccurrence of natural discharge after charging. Thus, wasteful use ofthe dry battery 48 can be prevented even if a user fails to turn off thecharger switch.

[0123] The operation of the above embodiment is described with referenceto FIG. 5. A flow is illustrated in FIG. 5, including steps from anphotographing operation at a user to a recycling operation at the end.

[0124] A camera manufacturer manufactures the lens-fitted photo filmunit 10 and the flash device 11. The flash device 11 is an externallyconnectable type. The lens-fitted photo film unit 10 can be used to takephotographs even without combining the flash device 11. Efficiency inthe manufacture can be high, because it is possible for the cameramanufacturer to reduce the types of lens-fitted photo film units forflash photography and daylight photography.

[0125] The lens-fitted photo film unit 10 and the flash device 11 areshipped by a camera manufacturer to photo shops, and supplied to users.The lens-fitted photo film unit 10 is sold in combination with the flashdevice 11 as a set, and also sold as a single product.

[0126] As the lens-fitted photo film unit 10 can be used without theflash device 11, a user who intends photographs without flash buys onlythe lens-fitted photo film unit 10. In contrast, another user whointends flash photography buys both the lens-fitted photo film unit 10and the flash device 11.

[0127] When the flash device 11 is secured to the lens-fitted photo filmunit 10, the sync switch segments 43 a and 43 b of the sync switch 43contact respectively the connection terminals 44 a and 44 b of the flashdevice 11, to connect the sync switch 43 to the flash circuit board 46.

[0128] When the sliding button 51 is slid to the on position, thecharger switch 57 is turned on to start charging the main capacitor 45.When the voltage across the main capacitor 45 being charged comes up tothe predetermined voltage level, then the LED 74 comes to illuminate toturn on the readiness indicator 52. Thus, a user is informed of thecompletion of the charging.

[0129] When the shutter release button 19 is depressed, the shutterblade 39 is knocked abruptly, to take an exposure on the photo film 24.When the shutter blade 39 comes to the open position, the sync switchsegments 43 a and 43 b are interconnected to turn on the sync switch 43.The trigger circuit 64 is operated to emit flash light.

[0130] When all frames in the photo film 24 are exposed, then the userbrings or forwards the lens-fitted photo film unit 10 to a photo shop,and requests printing to a photo finisher. The photo finisher receivesthe lens-fitted photo film unit 10 containing the photo film 24, andsubjects the photo film 24 to printing. The photo film 24 after beingdeveloped is returned to the user at the same time as photographicprints are supplied to him or her. The used body of the lens-fittedphoto film unit 10, in contrast, is withdrawn to the cameramanufacturer.

[0131] The flash device 11 can be used until the dry battery 48 is usedup. After this, a user removes the flash device 11 from the lens-fittedphoto film unit 10 and preserves for next use. He or she will buy anunused lens-fitted photo film unit 10 without the flash device 11. Theflash device 11 being preserved will be connected with the lens-fittedphoto film unit 10, and operated for exposures with flash light.

[0132] Thus, the flash device 11 can be used repeatedly. A user can takephotographs with flash by buying only the lens-fitted photo film unit 10at next time of exposure. Also, the flash device 11 is an externallyconnectable type. If a user desires photographs without flash, he or shecan buy the lens-fitted photo film unit 10 without buying the flashdevice 11. It is possible to reduce the cost per one photographaccording to the using manner of the user.

[0133] When the dry battery 48 in the flash device 11 is used up, nocharging can be effected. The readiness indicator 52 does notilluminate. A user is informed by this state of the readiness indicator52 that the dry battery 48 is used up.

[0134] The flash device 11 after using up the dry battery 48 iswithdrawn by photo finishers and forwarded to a camera manufacturer.Note that a user may bring the flash device 11 solely to a photofinisher without the lens-fitted photo film unit 10, and also may bringthe flash device 11 together with the lens-fitted photo film unit 10 toa photo finisher.

[0135] When the photo film 24 is completely used, the lens-fitted photofilm unit 10 is forwarded to a photo laboratory at a photo finisher. Incontrast, the flash device 11 can be used for a considerable number oftimes for an amount of plural photo film strips. Thus, the number offorwarding the flash device 11 to a photo laboratory is reduced incomparison with the known techniques. Distribution of the flash device11 to reloading dealers, part-reusing dealers or the like in the marketcan be suppressed. Unauthorized reloading or handling of parts orproducts can be reduced.

[0136] The lens-fitted photo film unit 10 does not include a flashdevice with a high cost. This will cause reduction of distribution ofthe used lens-fitted photo film units to a reloading dealer,part-reusing dealer or the like in the market. The proportion of genuinewithdrawal of the lens-fitted photo film unit 10 at the original cameramanufacturer can be higher. Therefore, the resources can be utilizedeffectively by reducing the abandonment. Pollution of the environmentcan be prevented.

[0137] The lens-fitted photo film unit 10 and the flash device 11withdrawn by the camera manufacturer are recycled in a suitable method.The flash device 11 is disassembled. Its parts are cleaned, inspected,and repaired if required. The parts are assembled again in a new flashcase with a new battery, and are reused. The used flash case ispelletized, and reused as regenerated plastic material. The used batteryis withdrawn by a specialized dealer, and recycled.

[0138] In the above embodiment, the connection terminals 44 a and 44 bfor connection with the sync switch 43 in the lens-fitted photo filmunit 10 are disposed on the surface of the retention projection 13outside the flash device 11. If the flash device 11 is removed from thelens-fitted photo film unit 10 after charging the main capacitor 45, itis likely that a users fingers touch erroneously the connectionterminals 44 a and 44 b, and receive electrical shock byshort-circuiting. The flash device 11 immediately after charging is verydangerous, as high voltage is applied to the connection terminals 44 aand 44 b in the same manner as the main capacitor 45. Consequently, itis desirable to dispose the connection terminals 44 a and 44 b in aposition hard to touch externally, for example in a rear surface oftongues of the retention projection 13.

[0139] Another preferred embodiment is described with reference to FIGS.6A and 6B, in which connection of a bayonet type is used. Elementssimilar to those in the above embodiments are designated with identicalreference numerals. A flash device 81 includes a flash case 82, in whichan engaging mechanism 83 is disposed on a case connection panel. For usewith this, a lens-fitted photo film unit 80 has a housing connectionpanel 84. There are a receiving opening 84 a as first gap portion, andan engaging groove 84 b for engagement with the engaging mechanism 83. Apair of retention projections 83 a as second portion are formed with theengaging mechanism 83, for engagement with the receiving opening 84 a. Aridge 83 b is formed on the periphery of the retention projections 83 afor engagement with the engaging groove 84 b. A pin 83 c as firstportion projects from the center of the engaging mechanism 83. Anengaging hole 84 c is formed in the center of the housing connectionpanel 84 for engagement with the pin 83 c.

[0140] Note that the lens-fitted photo film unit 80 can be used solely.If the housing connection panel 84 has a conspicuously projecting orretreating shape, neat appearance of the lens-fitted photo film unit 80is degraded by the housing connection panel 84. It is thus preferablethat a surface of the housing connection panel 84 is flush with asurface of the front and rear covers 31 and 32. Also, a protective covermay be added for covering the housing connection panel 84 in a mannerthe same as the above embodiment.

[0141] An O-ring 85 is fitted in the engaging groove 84 b. The O-ring 85tightens the fitted state between the engaging groove 84 b and the ridge83 b, and prevents entry of foreign matter into the lens-fitted photofilm unit 80 or the flash device 81, the foreign matter including dust,dirt, water and the like.

[0142] To connect the flash device 81, the flash device 81 is inclinedto position the retention projections 83 a for insertion into thereceiving opening 84 a. The engaging mechanism 83 is inserted into thereceiving opening 84 a, before the flash device 81 is rotated to a setposition. Thus, the engaging mechanism 83 is fixedly retained on thehousing connection panel 84, to connect the flash device 81 with thelens-fitted photo film unit 80.

[0143] A pair of contact points 86 a and 86 b are attached behind theretention projections 83 a, and connected with the trigger circuit. Thesync switch segments 43 a and 43 b are disposed inside the receivingopening 84 a of the housing connection panel 84, and constitutes thesync switch 43. When the engaging mechanism 83 is engaged with thereceiving opening 84 a, the contact points 86 a and 86 b come in contactwith the sync switch segments 43 a and 43 b.

[0144] The contact points 86 a and 86 b cannot be easily touched by afinger from outside, because located behind the retention projections 83a. This is effective in keep safety even when the flash device 81 isremoved from the lens-fitted photo film unit 80 after charging.

[0145] In the above embodiment, the trigger signal sent from thelens-fitted photo film unit from the flash device is electric. Anotherpreferred flash device 91 is depicted in FIGS. 7A and 7B, in which anoptical trigger signal of light is sent from a lens-fitted photo filmunit.

[0146] The flash device 91 includes an output light guide 92 of a synclight-emitting unit, and an input light guide 93 of a synclight-receiving unit. The flash device 91 has a flash case 91 a, havinga lateral panel where a first end 92 a of the output light guide 92 anda first end 93 a of the input light guide 93 appear. A second end 92 bof the output light guide 92 is disposed near to the LED 74 in thebooster 63, the LED 74 indicating readiness after charging. Light fromthe LED 74 is sent to the readiness indicator 52, and used as a triggersignal for the flash device 91.

[0147] The light from the LED 74 is passed through the output lightguide 92, and sent to the lens-fitted photo film unit. The light is thenpassed in synchronism with releasing of the shutter, passed through theinput light guide 93 and sent back to the flash device 91. A second end93 b of the input light guide 93 is disposed near to a photo receptorelement 98 as sync light-receiving unit. The photo receptor element 98is connected with the trigger circuit 64, sends an electric signal tothe trigger circuit 64 upon receiving the light from the input lightguide 93. A thyristor (not shown) is connected on a line of discharge ofthe trigger circuit 64. When the electric signal is input to the gate ofthe thyristor, then the thyristor is turned on. The trigger capacitorand the main capacitor are discharged to emit flash light.

[0148] The lens-fitted photo film unit has a sync switching device,which includes blade checking light guides 94 and 95. The blade checkinglight guide 94 has an input end 94 a which appears externally outsidethe lens-fitted photo film unit. The blade checking light guide 95 hasan output end 95 a which appears externally outside the lens-fittedphoto film unit. When the flash device 91 is connected with thelens-fitted photo film unit, the input end 94 a of the blade checkinglight guide 94 is opposed to the first end 92 a of the output lightguide 92. The output end 95 a of the blade checking light guide 95 isopposed to the first end 93 a of the input light guide 93.

[0149] There is a shutter blade 101 as shutter mechanism. Near to theshutter blade 101 are disposed an output end 94 b of the blade checkinglight guide 94 and an input end 95 b of the blade checking light guide95. The input end 95 b is opposed to the output end 94 b.

[0150] A movable sync segment 101 a is formed with the shutter blade101. When the shutter blade 101 is in the shut position, the movablesync segment 101 a is located between the output end 94 b of the bladechecking light guide 94 and the input end 95 b of the blade checkinglight guide 95, to intercept a light path from the output end 94 b tothe input end 95 b. When the shutter blade 101 rotates to the openposition, the movable sync segment 101 a comes away from the light path.The light exited from the output end 94 b comes incident upon the inputend 95 b, and then is directed back to the input light guide 93 in theflash device 91.

[0151] Therefore, the optical trigger signal of light is used and sentfrom the lens-fitted photo film unit to the flash device 91. Safety canbe kept because no uncovered contact points appear on the surface of theflash case 91 a.

[0152] In the above embodiment, the term of the use of the flash deviceis informed to users by means of discontinuation of illumination of thereadiness indicator 52 upon using up the battery. In FIG. 8A, a flashdevice 111 is illustrated, and includes a residue display panel 112 forinforming a user of the present availability of flash emission. Theresidue display panel 112 consists of an LCD (liquid crystal display)panel, and digitally indicates the number of times of flash emissionpossible as remainder. Therefore, the residue display panel 112 enablesa user to find information of possibility of using the flash device 111after the start of the use.

[0153] A predetermined number of flashing is stored in the flash device111 according to the useful life of relevant parts. The number offlashing is stepped decrementally at each time of flashing, so as toindicate the number of times of flashing possible as remainder. When theindicated number comes down to zero (0), the charging is disabled. Theflash device 111 becomes ineffective irrespective of existence or lackof residual capacity of the battery. It is unnecessary to determinecapacity of the battery according to the useful life of the parts.

[0154] In FIG. 9, a flash circuit board 114 for use with the residuedisplay panel 112 is illustrated. In FIG. 10, a flow of control of acounter/controller 116 for counting the number of times of flashemission is illustrated. The counter/controller 116 is connected withthe trigger circuit 64, and detects a current of discharge from thetrigger capacitor 68. Resistors 117 a and 117 b restrict a flow of thecurrent of the discharge toward the counter/controller 116. Arectification diode 118 prevents a reverse flow of the current of thedischarge. In a memory 110 of the counter/controller 116, apredetermined number of times of flash emission is stored. Upondetection of the current of the discharge, the counter/controller 116determines that the sync switch 43 is turned on, and steps down thecounted number by one, and outputs the number in the residue displaypanel 112.

[0155] A disabling transistor 119 as switching circuit has a base, withwhich the counter/controller 116 is connected. When the counted numberin the counter/controller 116 becomes zero (0), the counter/controller116 renders the disabling transistor 119 conductive. A collector of thedisabling transistor 119 is connected with the tertiary winding 62 c ofthe oscillation transformer 62. When the disabling transistor 119becomes conductive, a current from the tertiary winding 62 c flows inthe disabling transistor 119, so that the oscillation transistor 61becomes non-conductive and disables charging.

[0156] Instead of using the residue display panel 112, another preferredflash device 121 in FIG. 8B includes a residual amount indicator 122 asdisplay panel for indication in a stepwise manner Plural light-emittingdiodes (LEDs) 122 a are included in the residual amount indicator 122.The number of LEDs driven in the LEDs 122 a changes according to thecounted number.

[0157] While the lens-fitted photo film unit is unused, all the LEDs 122a emit light. According to emission of flash light, the counted numberdecreases, to turn off the LEDs 122 a serially. When the counted numbercomes down to zero (0), all the LEDs 122 a are turned off. Note that thenumber of the LEDs 122 a may be two, or four or more. Also, only onelight-emitting diode (LED) may be used. When the counted number becomesa predetermined limit number or lower, then the LED can be driven, toinform a user of a state with small residual life.

[0158] In the above embodiment, the residual amount indicator 122 may beset for illumination of all the three LEDs for an initially used stepwhen the number of times of the use is zero (0) or more and equal to orless than a predetermined number of times. However, it is possible inthe residual amount indicator 122 to illuminate at all the three LEDsfor an unused step when the number of times of the use is zero (0), andto illuminate at the two LEDs distinctly for an initially used step whenthe number of times of the use is one (1) or more and equal to or lessthan a predetermined number.

[0159] In the above embodiment, one LED in the residual amount indicator122 illuminates when the residual time number or number of times ofusability is one (1) or more and equal to or less than a predeterminednumber. All the LEDs are turned off in the residual amount indicator 122when the number of times of usability is zero (0). Alternatively, it ispossible in the residual amount indicator 122 to turn off all the LEDswhen the number of times of usability comes down to a predeterminedsmall number and until the number of times of usability comes down zero(0). Furthermore, the final step of the use, instead of beingrepresented by turning off all the LEDs, can be represented by turningon only one LED with appearance of expressing a small amount.

[0160] In the above embodiment, the flash device has the contact pointsfor sending the trigger signal from the lens-fitted photo film unit. Ashigh voltage is applied to the contact points immediately after thecharging, a user is likely to receive electric shock. The embodimentsdescribed heretofore are directed to the improvement of the position ofthe contact points, and the use of the optical trigger signal for thepurpose of not using contact points.

[0161] Still another preferred embodiment is described, in which dangerof electric shock can be avoided. In FIGS. 11A and 11B, a flash circuitboard 132 in a flash device 131 is provided with a charge allowingswitch 133 and a forcible discharging switch 134.

[0162] The charge allowing switch 133 is connected with the booster 63,and when the flash device 131 is connected with the lens-fitted photofilm unit, is turned on to allow the charging, and when the flash device131 is removed from the lens-fitted photo film unit, is turned off toinhibit the charging. The forcible discharging switch 134 is connectedin parallel with the main capacitor 45, and turned on when the flashdevice 131 is removed from the lens-fitted photo film unit, to dischargethe main capacitor 45. A resistor 136 is used for the discharge. Whenthe flash device 131 is connected with the lens-fitted photo film unit,the forcible discharging switch 134 is turned off.

[0163] In FIGS. 12A and 12B, the charge allowing switch 133 and theforcible discharging switch 134 are illustrated in detail. A lens-fittedphoto film unit 138 has a housing from which pressing projections 138 aand 138 b extend. A flash case of the flash device 131 is provided withinsertion holes 131 a and 131 b for receiving insertion of the pressingprojections 138 a and 138 b. The charge allowing switch 133 is disposedinside the insertion hole 131 a. The forcible discharging switch 134 isdisposed inside the insertion hole 131 b.

[0164] The charge allowing switch 133 includes contact points 133 a and133 b, and a movable segment 133 c for interconnecting the contactpoints 133 a and 133 b. The contact points 133 a and 133 b are connectedwith the flash circuit board 132. The movable segment 133 c is movablebetween an on position and off position, and when in the on position,contacts both the contact points 133 a and 133 b, and when in the offposition, comes away from the contact points 133 a and 133 b. Springs141 bias the movable segment 133 c toward the off position.

[0165] The forcible discharging switch 134 includes a pair of contactpoints 134 a and 134 b and a switch segment 134 c for interconnectingthe contact points 134 a and 134 b. The contact points 134 a and 134 bare connected with the flash circuit board 132. The switch segment 134 cis movable between on and off positions, and when in the on position,contacts the contact points 134 a and 134 b, and when in the offposition, comes away from the contact points 134 a and 134 b. Springs142 bias the switch segment 134 c toward the on position.

[0166] In FIG. 12A, the pressing projections 138 a and 138 b come intothe insertion holes 131 a and 131 b in the connected state of the flashdevice 131 with the lens-fitted photo film unit 138. The pressingprojection 138 a pushes the movable segment 133 c, and moves the same tothe on position against the bias of the springs 141. Therefore, thecharge allowing switch 133 is turned on to enable charging. Also, thepressing projection 138 b pushes the switch segment 134 c, and moves thesame to the off position against the springs 142. Thus, the forcibledischarging switch 134 is turned off.

[0167] When the flash device 131 is removed from the lens-fitted photofilm unit 138 as depicted in FIG. 12B, the pressing projections 138 aand 138 b are disengaged from the insertion holes 131 a and 131 b. Thedisengagement of the pressing projection 138 a causes the springs 141 tomove the movable segment 133 c to the off position. The charge allowingswitch 133 is opened to disable the charging. The disengagement of thepressing projection 138 b causes the springs 142 to move the switchsegment 134 c to the on position. Thus, the forcible discharging switch134 is turned on to discharge the main capacitor 45.

[0168] Therefore, discharging the main capacitor 45 upon removal of theflash device 131 is effective in preventing a user from feeling electricshock even he or she happens to touch the contact points of the syncswitch 43. The removal of the flash device 131 turns off the chargeallowing switch 133. So, if the charger switch is turned on, thereoccurs no restart of the charging. Also, if a user inadvertently failsto turn off the charger switch, there occurs no wasteful use of the drybattery 48.

[0169] It is also possible to use magnets for switching the chargeallowing switch 133 and the forcible discharging switch 134. In FIGS.13A and 13B, another preferred lens-fitted photo film unit 151 hasmagnets 151 a and 151 b for holding a flash device 152 by attraction.

[0170] When the flash device 152 is connected with the lens-fitted photofilm unit 151, the magnet 151 a contacts the contact points 133 a and133 b of the charge allowing switch 133, to interconnect those. Thecharge allowing switch 133 is turned on, to enable charging.

[0171] A first magnet 156 is fixed on the switch segment 134 c of theforcible discharging switch 134. The first magnet 156 and the magnet 151b are so disposed that their poles of the same polarity are opposed toeach other. When the flash device 152 is connected, the first magnet 156repels the magnet 151 b. The switch segment 134 c moves to the offposition against the springs 142, to turn off the forcible dischargingswitch 134.

[0172] When the flash device 152 is removed from the lens-fitted photofilm unit 151, the magnet 151 a comes away from the contact points 133 aand 133 b. The charge allowing switch 133 is turned off to disable thecharging. As the magnet 151 b as second magnet is away from the firstmagnet 156, the switch segment 134 c is caused by the springs 142 tomove to the on position, to turn on the forcible discharging switch 134.The main capacitor 45 is discharged.

[0173] Note that the magnets 151 a, 151 b and 156 may be permanentmagnets or electromagnets.

[0174] A flash circuit board 161 in FIG. 14 is characterized in loweredvoltage applied to the contact points for synchronization. A thyristor162 as trigger switching element is provided in the trigger circuit 64in the flash circuit board 161. An anode of the thyristor 162 isconnected with the common terminal of the trigger transformer 69. Acathode of the thyristor 162 is connected with a negative terminal ofthe trigger capacitor 68. A gate of the thyristor 162 is connected withone of the contact points of the sync switch 43.

[0175] A subsidiary trigger capacitor 163 is connected with a secondterminal of the sync switch 43. The subsidiary trigger capacitor 163stores charge input to a gate terminal of the thyristor 162. Thesubsidiary trigger capacitor 163 is charged by the booster 63 at thesame time as the main capacitor 45 and the trigger capacitor 68. Arectification diode 164 is connected for regulating a direction of acurrent.

[0176] The sync switch 43 is turned on, to discharge the subsidiarytrigger capacitor 163, to turn on the thyristor 162. Thus, the triggercapacitor 68 and then the main capacitor 45 are discharged. Flash lightis emitted.

[0177] The subsidiary trigger capacitor 163 has characteristically lowpotential even when fully charged, because of its purpose for turning onthe thyristor 162. Only the low voltage is applied to the sync switch43. This is effective in avoiding danger if a person s finger touchesthe sync switch 43. Also, the use of the charge allowing switch 133 cansuppress a restart of the charging after discharging while the flashdevice is removed.

[0178] In the above embodiment, flash light is emitted always after theflash device is charged. However, object brightness can be measured by aphotometric device. The flash emission can be controlled according tothe measured object brightness. Also, a flash device may have such anadjustable structure that an amount of flash light can be changedaccording to the object brightness.

[0179] Another preferred form of battery is depicted in FIG. 15. Thebattery is an electrode pin type 171. This form is effective insuppressing or preventing unwanted distribution of parts of the flashdevices. The battery 171 includes a battery body 172 and a pair ofbattery electrode pins 173 projecting from the battery body 172. A flashcircuit board 174 is connected with the battery 171 by means of thebattery electrode pins 173.

[0180] The battery 171 is fixed on the flash circuit board 174 byinserting the battery electrode pins 173 in through holes in the flashcircuit board 174 and attachment with solder. Therefore, the firmness inkeeping the battery 171 is very high on the flash circuit board 174. Ifthe battery 171 is removed with forcible operation, the batteryelectrode pins 173 are removed together with the battery body 172. Thisis effective in suppressing the reuse and distribution of the flashcircuit board 174 due to the difficulty in exchanging the battery 171.Specifically, the battery 171 can be constructed in a specialized form,so as to prevent users from easy exchange of the battery 171. Thus, theproportion of withdrawal of the flash device can be higher.

[0181] The battery electrode pins 173 of the battery 171 are disposed onone end of the battery body 172. This is effective in reducing a lengthof the battery electrode pins 173 in comparison with the form in whichelectrodes lie on ends of the battery body. It is possible to fix thebattery 171 firmly on the flash circuit board 174 in a manner resistantto detachment. Of course, a battery in which electrodes lie on ends ofthe battery body may be used in combination with the flash circuit board174.

[0182] In FIGS. 16A-20, another preferred embodiment is depicted, inwhich a flash device is externally connectable, but a battery iscontained in a housing of a lens-fitted photo film unit. Elementssimilar to those of the above embodiments are designated with identicalreference numerals. In FIGS. 16A and 16B, a lens-fitted photo film unit210 is used in combination with a flash device 211. Those constitute alens-fitted photo film system 209. The lens-fitted photo film unit 210has a mechanism for taking an exposure and is pre-loaded with photofilm. The flash device 211 is an externally connectable type, and issecured to the lens-fitted photo film unit 210 in a removable manner.

[0183] The lens-fitted photo film unit 210 is a single-use device inwhich the photo film is used only for one time. The flash device 211, incontrast, is a repeatedly usable device for plural strips of the photofilm, and has a considerably long useful life. A dry battery 248 isaccommodated in the lens-fitted photo film unit 210 for supplying theflash device 211 with power.

[0184] A user can connect the flash device 211 with an unusedlens-fitted photo film unit 210 in place of the lens-fitted photo filmunit 210 after the use, and can take photographs with those. It isimpossible to exchange the photo film in the lens-fitted photo film unit210. Capacity of the dry battery 248 is predetermined at a levelsufficient for exposures of a single strip of the photo film. Thus, thedry battery 248 can be AAA type, and other types with a considerablysmall capacity. This can reduce the size of the whole of the lens-fittedphoto film unit 210.

[0185] In FIGS. 17 and 18, an attachment engaging projection 212 asattaching portion is formed to project from a lateral panel of thelens-fitted photo film unit 210, for connection of the flash device 211in a removable manner. The attachment engaging projection 212 projectshorizontally. Positioning ridges 212 a are formed on the top of theattachment engaging projection 212. A retention gap 212 b is formedbetween the positioning ridges 212 a for keeping the flash device 211from dropping accidentally. An output connector 213 is disposed underthe positioning ridges 212 a for electric connection with the flashdevice 211.

[0186] An engaging recess 214 as engaging portion is formed in the flashdevice 211 for engagement with the attachment engaging projection 212.The engaging recess 214 retreats in association with the shape of theattachment engaging projection 212. An inner surface of the engagingrecess 214 is formed for engagement with the positioning ridges 212 aand the retention gap 212 b. An input connector 215 is disposed in theengaging recess 214 for connection with the output connector 213. Theflash device 211 is attached to the lens-fitted photo film unit 210 byretaining the attachment engaging projection 212 with the engagingrecess 214.

[0187] Four male terminals 213 a as first and second connectionterminals are included in the output connector 213. Two of the maleterminals 213 a are a pair used with a sync switch. The remaining two ofthe male terminals 213 a are a pair used for supply of power. Fourfemale terminals 215 a as powering terminals and trigger terminals areincluded in the input connector 215, and connectable with the maleterminals 213 a. The female terminals 215 a are shaped to receiveinsertion of the male terminals. The flash device 211 is supplied withpower, and also receives a trigger signal, both through the outputconnector 213 and the input connector 215.

[0188] It is to be noted that the shapes of the attachment engagingprojection 212, the engaging recess 214, the output connector 213, theinput connector 215, the male terminals 213 a and the female terminals215 a are not limited to those described above, but can be any suitableone of various forms.

[0189] In FIG. 19, a pair of sync switch segments 243 a and 243 b havefirst ends which are disposed near to a shutter blade 239. A terminalholder 250 supports second ends of the sync switch segments 243 a and243 b. To be precise, the male terminals 213 a are supported by theterminal holder 250 inclusive of the sync switch segments 243 a and 243b. As a method of fixation, an in-mold forming is used to attach thesync switch segments 243 a and 243 b to the terminal holder 250. A rollholder chamber 223 b has an upper face where the terminal holder 250 issecured.

[0190] The dry battery 248 is disposed under an exposure unit 233.Contact segments of metal (not shown) are disposed under the exposureunit 233 for contact with electrodes of the dry battery 248. The contactsegments are connected with the male terminals 213 a.

[0191] The flash device 211 is constituted by a flash circuit board 246,a flash emitter 247 and a flash case 249. The flash circuit board 246has a circuit pattern printed on a substrate, and includes variouscircuit elements in which a main capacitor 245 is included. The flashemitter 247 has a xenon discharge tube, a reflector, a diffusing plateand the like. The flash case 249 contains any of those elements. Forthose parts to be assembled in the flash device 211, parts with betterperformance and higher durability than those of a flash built-in type oflens-fitted photo film unit known in the prior art are used. Amanufacturing cost of the flash device 211 is relatively higher. Anexpense of a user buying the flash device 211 may be high. However, theflash device 211 can be used for many times. A cost paid for the use canbe lower in consideration of expense per one time of flashing.

[0192] A diffusing plate for the flash emitter 247 appears in the frontpanel of the flash case 249. A charger button 251 is disposed under thediffusing plate. A rear of the charger button 251 contacts a chargerswitch included in a flash circuit. Only while the charger button 251 isdepressed, an operation of charging is continued. This is advantageousin that no operation of turning off is required. No wasteful use of thedry battery 248 occurs. Note that a charger button of a latch type maybe used, and kept positioned in the on state. Also, a sliding type ofoperation member may be used in place of the pushbutton.

[0193] The lens-fitted photo film unit 210 does not contain an expensiveflash device. Used sets of the lens-fitted photo film unit 210 areprevented from distribution to reloading dealers, part-reusing dealersor the like in the market. The proportion of genuine withdrawal of thelens-fitted photo film unit 210 at the original camera manufacturer canbe higher. Therefore, the resources can be utilized effectively byreducing the abandonment. Environmental pollution can be prevented.

[0194] In the above embodiment, the male terminals 213 a and the femaleterminals 215 a are used for connecting the flash device 211 with thelens-fitted photo film unit 210. However, each of the two sets of theterminals may include three terminals. The three may include a poweringterminal, a trigger terminal and a common terminal for both of poweringand triggering.

[0195] In the above embodiment, the dry battery 248 is used as a powersource for driving the flash device 211. However, the dry battery 248may be used for supplying power to an aperture stop changing mechanism,which may be incorporated in the lens-fitted photo film unit 210 forchanging over an aperture stop according to measured object brightness.

[0196] In FIGS. 21A-24, still another preferred embodiment isillustrated, in which one housing can be used for two types oflens-fitted photo film units. Elements similar to those of the aboveembodiments are designated with identical reference numerals. In FIGS.21A, 21B and 22, a lens-fitted photo film unit 302 of a flash typeincludes a housing 304, which is commonly usable as an element in alens-fitted photo film unit 303 of a daylight type. The housing 304 hasa mechanism for taking an exposure and is pre-loaded with photo film. Anattaching recess 307 as attaching portion or containing gap is formed inthe housing 304. A flash device 306 of an externally connectable type issecured to the attaching recess 307 in a removable manner.

[0197] When the flash device 306 is retained in the attaching recess307, the lens-fitted photo film unit 302 of the flash type is obtained.A dummy block 308 or dummy cover can be attached also to the attachingrecess 307 in place of the flash device 306. The dummy block 308 is acover f or covering the attaching recess 307 at the time of not usingthe flash device 306. The lens-fitted photo film unit 303 of thedaylight type is obtained when the dummy block 308 is attached. Thehousing 304 for the lens-fitted photo film units 302 and 303 is utilizedas a common element. This is effective in raising efficiency in theproduction in a factory.

[0198] In FIG. 24, the lens-fitted photo film unit 302 is viewed in ahorizontal section. The attaching recess 307 is formed by recessing aportion of a front cover 331 as outer cover. An engaging groove 307 a isformed in a wall of the attaching recess 307. An engaging portion 306 aof the flash device 306 and an engaging portion 308 a of the dummy block308 are engaged with the attaching recess 307. Switch segments 343 a and343 b of metal are partially located inside the engaging groove 307 a.Contact points 344 a and 344 b appear on the outside of the engagingportion 306 a of the flash device 306 for connection with the switchsegments 343 a and 343 b. When the engaging portion 306 a is engagedwith the engaging groove 307 a, the switch segments 343 a and 343 b comein contact with respectively the contact points 344 a and 344 b.

[0199] A flash case 349 is included in the flash device 306, andconstitutes a portion of an outer surface of the lens-fitted photo filmunit 302 together with the front cover 331. Namely, a portion of theflash case 349 appears outside the lens-fitted photo film unit 302 in amanner flush with the front cover 331.

[0200] The dummy block 308 is formed in an approximately equal shape tothe flash case 349 of the flash device 306. According to this, aperipheral contour of the lens-fitted photo film unit 302 of the flashtype can be determined approximately the same as a peripheral contour ofthe lens-fitted photo film unit 303 of the daylight type. Packagingmaterial such as a gusseted bag for packaging the lens-fitted photo filmunits 302 and 303 can be commonly prepared. This is advantageous inkeeping high efficiency in production, as the number of the types ofpackaging materials can be reduced.

[0201] A peripheral contour of the flash case 349 is approximately thesame as a peripheral contour of the dummy block 308. To produce those,it is possible to use molds which are partially the same. Although moldsin general are very expensive in the manufacturing cost, the commonportions in the molds for the flash case 349 and the dummy block 308make it possible to lower the cost. Also, a shape or design of a contouror appearance can be commonly created between the lens-fitted photo filmunit 302 of the flash type and the lens-fitted photo film unit 303 ofthe daylight type. The number of the shapes or designs to be produced isreduced. This can reduce the cost in development of goods to be shippedto the market.

[0202] In FIGS. 25 and 26, another preferred lens-fitted photo film unit371 is illustrated, in which an attaching recess 373 as attachingportion or containing gap is formed in a lateral portion of a housing372. A flash device 374 has a flash case 376, which is shaped toconstitute a greater part of the lateral portion of the lens-fittedphoto film unit 371. A front cover 377 as outer cover includes theattaching recess 373. There is a dummy block 378 used when the flashdevice 374 is not used. The dummy block 378 covers the attaching recess373. The dummy block 378 has a shape approximately the same as that ofthe flash device 374.

[0203] To locate the attaching recess 373 on a lateral end of thehousing 372, a roll holder chamber 375 b of a housing 375 is locatedrather close to a light-shielded tunnel 379. The flash device 374 isdisposed beside the roll holder chamber 375 b. Therefore, it is possibleto reduce a front-to-back thickness of the lens-fitted photo film unit371. Also, a flash circuit board 346 in the flash case 376 may bedisposed in parallel with a lateral face of the flash case 376. This canreduce a width of the flash device 374, and can suppress enlargement inthe width of the lens-fitted photo film unit 371.

[0204] In the above embodiments, a selected one of the flash device 306,374 and the dummy block 308, 378 is fitted on the front cover 331, 377.In FIGS. 27A and 27B, another preferred lens-fitted photo film unit 381is depicted. A flash case 384 of a flash device 383 is formed with afront cover 382 as a portion of a single piece. For the structure of theflash type, a front of a housing 386 is utilized as a portion forattachment. For the structure of the daylight type without the flashdevice 383, a front cover 388 as outer cover is secured to the housing386 in a simple shape without the flash case 384. According to this, aperipheral contour of the flash type can be approximately the same as aperipheral contour of the daylight type, because the front of thehousing 386 is totally covered inside.

[0205] In the embodiment illustrated in FIGS. 8A-10, durability of theparts of the flash device is relatively low by selection of thematerial. This is effective in lowering the manufacturing cost becauseof a short useful life. In other words, the time of the useful lifeelapses while there remains residual capacity in the battery. Incontrast, according to all the remaining embodiments, the battery isdetermined to have a small capacity to lower the manufacturing cost. Inother words, the residual capacity of the battery comes down to zero inthe course of repeated flash emission before lapse of the useful time ofthe parts.

[0206] However, the features of the embodiment in FIGS. 8A-10, namelythe residue display panel 112, the counter/controller 116 and thedisabling transistor 119, may be combined in the other embodiments.Thus, it is possible to produce parts with lower durability incombination of a battery with sufficient capacity equal to that of awidely used battery. This is effective in lowering the manufacturingcost.

[0207] Although the present invention has been fully described by way ofthe preferred embodiments thereof with reference to the accompanyingdrawings, various changes and modifications will be apparent to thosehaving skill in this field. Therefore, unless otherwise these changesand modifications depart from the scope of the present invention, theyshould be construed as included therein.

What is claimed is:
 1. A flash device for a lens-fitted photo film unitpre-loaded with unexposed photo film, comprising: a main capacitor forstoring charge; a flash emitter for emitting flash light upondischarging said main capacitor; a flash circuit board for controllingcharging and discharging of said main capacitor; a battery for supplyingsaid flash circuit board with power; a tightly closed flash case,secured to said lens-fitted photo film unit, for containing saidbattery, said main capacitor, said flash emitter and said flash circuitboard.
 2. A flash device as defined in claim 1, wherein said lens-fittedphoto film unit includes a sync switch for becoming conductive insynchronism with an exposure, to discharge said main capacitor; furthercomprising first and second connection terminals, disposed outside saidflash case, for connection with said sync switch.
 3. A flash device asdefined in claim 2, wherein voltage across said main capacitor isprevented from application to said first and second connection terminalswhile said flash case is away from said lens-fitted photo film unit. 4.A flash device as defined in claim 3, wherein said flash emitterincludes a flash discharge tube having a trigger electrode; said flashcircuit board includes a trigger circuit having: a trigger capacitor forbeing charged together with said main capacitor, and for beingdischarged upon turning on of said sync switch; a trigger transformer,having primary and secondary windings, said primary winding beingconnected with said trigger capacitor, said secondary winding beingconnected with said trigger electrode, said trigger transformergenerating high voltage upon discharge of said trigger capacitor byboosting voltage across said trigger capacitor, to apply said highvoltage to said trigger electrode, to start light emission of said flashdischarge tube.
 5. A flash device as defined in claim 1, wherein saidflash circuit board includes: a memory for storing information of auseful life flashing time number of times of emitting flash light insaid flash emitter; a counter for counting a flashing time number oftimes of emitting flash light in said flash emitter; and a switchingcircuit for inhibiting operation of said flash emitter in response toreach of said flashing time number to said useful life flashing timenumber.
 6. A flash device as defined in claim 5, further comprising adisplay device for displaying information of a present flash usabilityaccording to said flashing time number and said useful life flashingtime number.
 7. A flash device as defined in claim 6, wherein said flashusability information comprises a number of usable times according to adifference of said useful life flashing time number and said flashingtime number.
 8. A flash device as defined in claim 6, wherein saiddisplay device includes plural light sources, and is changeable in anumber of light sources being driven according to one of ranks of anumber of usable times defined by a difference between said useful lifeflashing time number and said flashing time number.
 9. A flash device asdefined in claim 1, wherein said lens-fitted photo film unit includes ahousing connection panel having a receiving opening opposed to saidflash case; further comprising a retention projection, formed to projectfrom a case connection panel of said flash case opposed to said housingconnection panel, fitted in said receiving opening, for retaining saidcase connection panel on said housing connection panel.
 10. A flashdevice as defined in claim 9, wherein said receiving opening includes: afirst gap portion; and a second gap portion, disposed to extend fromsaid first gap portion, and having a greater width than said first gapportion; said retention projection includes; a first portion, disposedto project from said case connection panel, for being inserted in saidfirst gap portion; and a second portion, disposed at an end of saidfirst portion to project in a widening direction, for being engaged withan inside of said first gap portion, to keep said first portion fromdropping, said second portion being inserted into said second gapportion before engagement of said first portion with said first gapportion.
 11. A flash device as defined in claim 10, wherein afterinsertion into said second gap portion, said second portion is engagedwith said first gap portion by sliding or rotating said retentionprojection relative to said receiving opening.
 12. A flash device asdefined in claim 1, wherein said lens-fitted photo film unit includes: ashutter mechanism, having a shutter blade, for providing said photo filmwith an exposure; first and second blade checking light guides, disposedso that an output end of said first light guide thereof and an input endof said second light guide thereof are positioned opposite to oneanother with respect to said shutter blade in a back-to-front direction,wherein said first and second light guides, when said shutter blade isclosed, are in an optical intercepting state, and when said shutterblade is open, are in an optical transmitting state; said flash circuitboard further includes: a sync light-emitting unit for supplying a lightsignal through an input end of said first light guide; a synclight-receiving unit for detecting said light signal emitted externallyfrom an output end of said second light guide when in said opticaltransmitting state, and for generating a trigger signal; and a triggercircuit for discharging said main capacitor in response to said triggersignal.
 13. A flash device as defined in claim 1, further comprising acharge allowing switch for being changed over in response to connectionand detachment between said flash case and said lens-fitted photo filmunit, to allow charging of said main capacitor upon connection of saidflash case, and to inhibit charging of said main capacitor upondetachment of said flash case.
 14. A flash device as defined in claim13, further comprising a forcible discharging switch, connected withsaid main capacitor, for being changed over in response to connectionand detachment between said flash case and said lens-fitted photo filmunit, to allow charging operation of said main capacitor upon connectionof said flash case, and forcibly to discharge said main capacitor upondetachment of said flash case.
 15. A flash device as defined in claim14, wherein said forcible discharging switch includes: a pair of contactpoints; and a switch segment for being moved by connection with anddetachment from said lens-fitted photo film unit; said switch segment,when said flash case is connected with said lens-fitted photo film unit,is away from said pair of said contact points, and when said flash caseis away from said lens-fitted photo film unit, contacts said pair ofsaid contact points.
 16. A flash device as defined in claim 14, whereinsaid forcible discharging switch includes: a pair of contact points; aswitch segment for contacting said pair of said contact points when saidflash case is detached therefrom; a first magnet, secured to said switchsegment, and opposed to said lens-fitted photo film unit; wherein saidlens-fitted photo film unit includes a second magnet for repelling andshifting said first magnet when flash case is connected therewith, toseparate said switch segment from said pair of said contact points. 17.A flash device as defined in claim 1, wherein said flash emitterincludes a flash discharge tube having a trigger electrode; said flashcircuit board includes a trigger circuit having: a trigger capacitor forbeing charged together with said main capacitor; a trigger transformer,having primary and secondary windings, said primary winding beingconnected with said trigger capacitor, said secondary winding beingconnected with said trigger electrode, said trigger transformergenerating high voltage upon discharge of said trigger capacitor byboosting voltage across said trigger capacitor, to discharge said maincapacitor; a trigger switching element, having an anode, a cathode and agate, said anode being connected with a common terminal of said primaryand secondary windings, said cathode being connected with said triggercapacitor; when a sync switch is turned on in said lens-fitted photofilm unit in synchronism with an exposure, said trigger signal is inputto said gate of said trigger switching element, so that said triggerswitching element becomes conductive to discharge said triggercapacitor.
 18. A flash device as defined in claim 1, wherein said flashcircuit includes first and second battery connection terminals; saidbattery includes first and second battery electrodes, disposed to extendin one common direction, and connected with respectively said first andsecond battery connection terminals fixedly.
 19. A lens-fitted photofilm unit comprising: a housing pre-loaded with unexposed photo film; aflash device for emitting flash light; an attaching portion, formed withsaid housing, and adapted to securing of said flash device in aremovable manner; a battery, contained in said housing, for supplyingsaid flash device with power.
 20. A flash device for a lens-fitted photofilm unit in which an unexposed photo film is pre-loaded and a batteryis contained, comprising: a flash emitting circuit for emitting flashlight; and a powering terminal, connected with said battery, forsupplying said flash emitting circuit with power.
 21. A lens-fittedphoto film system, having a lens-fitted photo film unit, and a flashdevice for emitting flash light at a time of an exposure with flashlight; said lens-fitted photo film unit including: a housing pre-loadedwith unexposed photo film; an attaching portion, formed on said housing,and adapted for removable securing of said flash device; a batterycontained in said housing; a first connection terminal, positionedoutside said housing, for supplying power from said battery; said flashdevice including: a flash emitter for emitting flash light; a flash casefor containing said flash emitter, having a connection panel for beingsecured to said attaching portion in a removable manner; and a poweringterminal, disposed outside said connection panel, connected with saidfirst connection terminal, for being supplied with power by saidlens-fitted photo film unit.
 22. A lens-fitted photo film system asdefined in claim 21, wherein said housing is box-shaped, and has a frontpanel, a rear panel, and first and second lateral panels; said firstlateral panel has said attaching portion.
 23. A lens-fitted photo filmsystem as defined in claim 22, wherein said lens-fitted photo film unitfurther includes: a sync switch, incorporated in said housing, forgenerating a trigger signal in synchronism with an exposing operation,wherein said flash emitter is caused by said trigger signal to emitflash light; and a second connection terminal, arranged beside saidfirst connection terminal, for outputting said trigger signal from saidsync switch; said flash device further includes a trigger terminal,arranged beside said powering terminal, for connection with said secondconnection terminal.
 24. A lens-fitted photo film system as defined inclaim 23, wherein said first and second connection terminals are maleterminals; said trigger terminal and said powering terminal are femaleterminals.
 25. A lens-fitted photo film system as defined in claim 24,wherein said connection panel includes an engaging portion, engaged withsaid attaching portion of said first lateral panel.
 26. A lens-fittedphoto film system as defined in claim 25, wherein said attaching portionincludes an engaging projection, and said engaging portion includes anengaging recess.
 27. A lens-fitted photo film system as defined in claim26, wherein said attaching portion further includes at least onepositioning ridge disposed to project from an edge of said engagingprojection; said engaging portion further includes at least onepositioning notch, formed in an edge of said engaging recess, andengaged with said positioning ridge.
 28. A lens-fitted photo film unitcomprising: a housing pre-loaded with unexposed photo film; a flashdevice for emitting flash light; an attaching portion, formed with saidhousing, and adapted to securing of said flash device in a removablemanner; and said attaching portion being used for securing a dummy blockin producing a daylight type lacking said flash device.
 29. Alens-fitted photo film unit as defined in claim 28, wherein said flashdevice includes: a flash emitter having a flash discharge tube; a flashcircuit board for causing said flash discharge tube to illuminate insynchronism with an exposing operation; a battery for supplying saidflash circuit board with power; and a tightly closed flash case forcontaining said flash emitter, said flash circuit board, and saidbattery.
 30. A lens-fitted photo film unit as defined in claim 29,wherein said housing includes: a main body pre-loaded with saidunexposed photo film; a front cover secured to a front of said mainbody; a rear cover secured to a rear of said main body; a recess, formedin said front cover to constitute said attaching portion, for beingfitted on a selected one of said flash device and said dummy block. 31.A lens-fitted photo film unit as defined in claim 30, wherein an outersurface of said flash device or said dummy block lies in an extension ofa surface of said front cover.
 32. A lens-fitted photo film unit asdefined in claim 31, wherein said recess and said flash device areL-shaped as viewed downwards.
 33. A lens-fitted photo film unit asdefined in claim 31, wherein said recess and said flash device aresubstantially box-shaped.
 34. A flash device for a lens-fitted photofilm unit including a main body pre-loaded with unexposed photo film,and an outer cover for covering an outside of said main body, said flashdevice comprising: a flash emitter having a flash discharge tube; aflash circuit board for causing said flash discharge tube to illuminatein synchronism with an exposing operation; a battery for supplying saidflash circuit board with power; a tightly closed flash case forcontaining said flash emitter, said flash circuit board and saidbattery; wherein said flash case is removably secured to an attachingportion formed on said outer cover, and has a surface on an extension ofan outer surface of said outer cover.
 35. A lens-fitted photo film unitincluding a main body pre-loaded with unexposed photo film, and an outercover for covering an outside of said main body, said lens-fitted photofilm unit comprising: a flash emitter having a flash discharge tube; aflash circuit board for causing said flash discharge tube to illuminatein synchronism with an exposing operation; a battery for supplying saidflash circuit board with power; a tightly closed flash case forcontaining said flash emitter, said flash circuit board and saidbattery, said flash case being formed with an inside of said outercover.
 36. A lens-fitted photo film unit pre-loaded with unexposed photofilm, comprising: a main body for containing said photo film; a rearcover secured to a rear of said main body; a flash type of front cover,secured to a front of said main body; and a tightly enclosed flashdevice, secured to a rear of said front cover, for emitting flash lightin an exposure of flash photography.
 37. A lens-fitted photo film unitas defined in claim 36, wherein said flash device includes a battery.38. A lens-fitted photo film unit as defined in claim 37, furthercomprising a daylight type of front cover lacking said flash device,wherein a selected one front cover of said flash type and said daylighttype is designated in course of manufacture, and is secured to said mainbody.